Seat belt tension sensor

Abstract

A seat belt tension sensor assembly including magnets oriented to reduce assembly size comprises a pull plate having portions defining a belt loop opening for receiving seat belt webbing and a sensor opening. First and second magnets are coupled to the pull plate on opposite sides of the sensor opening and are oriented with a first pole adjacent the sensor opening and second pole positioned away from the opening toward a side of the sensor assembly. A sensor disposed in the sensor opening is configured to provide an output in response to flux imparted thereto by the magnets. At least one projection extends from the sensor opening of the pull plate generally towards the sensor and is configured to direct magnetic flux from the magnets in a closed-loop path through the sensor. Upon application of tension to the seat belt webbing, the pull plate is configured to move along a first axis of the seat belt tension sensor assembly relative to the sensor. The output of the sensor is indicative of a level of the tension.

1. A seat belt tension sensor assembly comprising:
 a pull plate having portions defining a belt loop opening for receiving seat belt webbing and a sensor opening; 
 first and second magnets coupled to said pull plate on opposite sides of said sensor opening, each of said first and second magnets being oriented with a first pole adjacent said sensor opening and second pole positioned away from said opening toward a side of said sensor assembly; 
 a sensor at least partially disposed in said sensor opening, said sensor being configured to provide an output in response to flux imparted thereto by said first and second magnets, and 
 at least one projection extending from a side of said sensor opening generally towards said sensor, said at least one projection configured to direct magnetic flux from said first and second magnets through said sensor; 
 whereby upon application of tension to said seat belt webbing, said pull plate is configured to move along a first axis of said seat belt tension sensor assembly relative to said sensor, said output of said sensor being indicative of a level of said tension. 
 
     
     
       2. A sensor according to  claim 1 , said sensor comprising a protective cover disposed over at least a portion of said pull plate. 
     
     
       3. A sensor according to  claim 1  wherein said first and said second magnets move relative to said sensor. 
     
     
       4. A sensor according to  claim 1  wherein said first and said second magnets each comprise a longitudinal axis extending through said first and said second poles and wherein said first and said second magnets are each arranged such that said longitudinal axis are substantially perpendicular to said first axis. 
     
     
       5. A sensor according to  claim 4  wherein said first and said second magnets remain at a substantially constant distance from said sensor upon application of tension to said seat belt webbing. 
     
     
       6. A sensor according to  claim 1  comprising a first and a second projection extending generally towards said sensor from a first and a second generally opposite side of said sensor opening of said pull plate, respectively. 
     
     
       7. A sensor according to  claim 6  wherein said first and said at least a second projection extending from said first and said second sides of said sensor opening generally along said first axis. 
     
     
       8. A sensor according to  claim 1  wherein said pull plate is configured to form a closed loop magnetic return. 
     
     
       9. A seat belt tension sensor assembly comprising:
 a pull plate having portions defining a belt loop opening for receiving seat belt webbing and a sensor opening for receiving a sensor; said pull plate configured to move along a first axis of said seat belt tension sensor assembly relative to said sensor; 
 a sensor at least partially disposed in said sensor opening and configured to be stationary with respect to said pull plate; 
 a first and a second magnet coupled to said pull plate on opposite sides of said sensor opening, wherein said first and said second magnets each comprise a longitudinal axis extending through a first and a second pole and wherein said first and said second magnets are each arranged such that said longitudinal axis are substantially perpendicular to said first axis; and 
 a first and at least a second projection extending generally towards said sensor from a first and a second generally opposite side of said sensor opening of said pull plate, respectively, said first and said at least a second projection configured to direct magnetic flux from said first and second magnets in a closed-loop path through said sensor. 
 
     
     
       10. A sensor according to  claim 9  wherein said first and said at least a second projection extend from said first and said second sides of said sensor opening generally along said first axis. 
     
     
       11. A sensor according to  claim 10  wherein said first and said second magnets remain at a substantially constant distance from said sensor upon application of tension to said seat belt webbing. 
     
     
       12. A sensor according to  claim 11  wherein said pull plate is configured to form a closed loop magnetic return.